If you need an icos as .ico file, you need not install any specific software in your system. There are lot of online tools which can be generate .ico files instantly for your desired sizes. Here are some top most websites listed for ico files.
Favicon Generator provides an easy way to convert and GIF, PNG or JPEG to ICO which is supported by all modern web browsers.
Use this online tool to easily create a favorites icon (favicon) for your site. Capable of generating desktop icons as well.
favicon.cc is a tool to create or download favicon.ico icons, that get displayed in the address bar of every browser.
An online favicon editor by Steven DeGraeve, which also offers the option to generate afavicon from an uploaded PNG image.
Favigen is a favicon generator which will allow the user to create a favicon for their website.
Antifavicon creates your text as text favicons in different colors.